What Goes Into Seed Coatings? Seed Coating Materials and What They Do

More and more farmers are turning to seeds that utilize seed coating technology and it’s becoming one of the fastest-growing (and most successful) modern ag tech innovations today. It’s also true that seed companies are starting to use seed coatings or pelleting on their products: it’s only a matter of time until seed coating or pelleted seed becomes an industry standard for seed companies and operations of all types.

When you purchase coated, pelleted, or otherwise treated seed, what goes into seed coatings? We take a look at the most widespread seed coating materials and what they do.

Polymers

According to the 2022 Global Seed Coating Market report, polymers are the most widely used seed coating technology among companies. This is because they accomplish many of seed coatings’ purposes: enhancing seed uniformity (and thus planting and seedling success), improving handling, and protecting the seed inside from outside elements such as excess moisture, dust, and disease.

Some examples of seed coating polymers are chitosan, polyvinyl, and polyethylene glycol. These also adhere well to other seed coating materials serving other purposes (keeping materials “stuck” to the seed), assisting in keeping these materials close— or separate— from the seed surface, depending on what the material’s purpose may be.

Minerals

Plant mineral micronutrients like iron, zinc, magnesium, phosphorus, and others may feature in some seed coatings. These give germinating seeds a “boost” while also providing early-stage seedlings with their micronutrient needs from the get-go— thus ensuring more successful yields and profits in the long run.

Minerals in seed coatings may provide improved general nutrient composition or pH adjustment for soils in some contexts. This may be helpful to the farmer when targeted and regularly done. Mineral materials are usually provided and applied as part of coatings in a powder form. A polymer or a binder may then be applied to keep the mineral powder adhered to the seed so it is only released when planted and germinated.

Colorants

You may find some seed coatings in markedly vivid colors: like red, pink, green, or yellow. These are due to colorants added to seed coatings for improving seed visibility, which can be helpful to producers during the planting stage: vibrant colors make seeds easier to spot and thus optimal plant spacing can be achieved. Some bright colors can also be off-putting to animals and insect pests that may want to consume them as well (especially birds).

In most cases, colorants are made from natural materials incorporated into the seed coating. Some examples include riboflavin, fluorescein, rhodamine, and others.

Binders

Typically composed of naturally sourced materials, binders have similar purposes to polymers when it comes to their seed coating technology benefits. They adhere other materials to the seed while also sealing out unwanted moisture, dust, and other elements. Some binders may also help raise seed germination rates.

The most commonly used binders for seed coating found in the industry are arabic gum, soy flour, or polyvinyl alcohol. Some others also include methyl cellulose or carboxymethyl cellulose. Of note, some binders are necessary for the application of other seed coating materials— for example, microbial agents containing bacteria or fungi are known to establish more successfully with help of a binder, as the binders help the microbes survive.

Microbial agents

Soil microbes, which may be bacterial or fungal, are shown to enhance nutrient absorption at plant roots. They can also help make certain nutrients more bioavailable in soils.

The most common type of microbial agent incorporated into seed coating technology is Rhizobia bacteria, the microbe needed for nitrogen fixation to occur in soil. Naturally this microbial agent is added to legume seed coatings— such as alfalfa, soy, red clover, peas, and others— to boost legume nitrogen fixing capabilities.

Some research also shows microbes may help raise the drought tolerance of seedlings exposed to them. For microbial agents to be utilized in seed coatings (such as in the chase of Rhizobia), strains are bound (with a binder) that is adhesive and also includes a carbon source to help protect, feed, and keep the bacteria alive until the seed is ready to be planted. Binders like peat and biochar are the most widely used for this purpose.

Growers should avoid storing seed in areas that are excessively dry or hot, which can then endanger the lifespan and success of the microbial agent.

Protective chemicals

Disease can be one of the greatest threats to seed viability and seedling vigor. As such, many seed coatings also incorporate a pesticide or fungicide to bring an added layer of protection for your crops’ earliest life stage, in addition to the protective benefits of polymers or binders.

Some popular protective chemicals may be “biopesticides” and more naturally based— such as Spinosad, which can repel insect pests. However, the wider standard found among seed coatings tends to be the typical chemical pesticide and fungicide applications farmers also use on established crops.

Have Questions?

Many farmers use seed coatings or pelleted seed, but are curious about their contents and materials, and what each might do. Contact us at Summit Seed with your questions today.